Are bottlenose dolphins of the Northern Gulf of Mexico migratory? Or do they live out their lives within the local waters?
Bottlenose dolphins primarily can be divided into two groups: coastal and offshore. Coastal bottlenose dolphins are often bay, sound and estuary residents who live close to shore and have small home ranges. On the other hand, offshore bottlenose dolphins, or “transients,” may travel along the coast, with some in the Atlantic known to seasonally migrate.
However, the animals in our area are not yet known to be migratory in this way (best documented for higher-latitude beasts). Our work in the Northern Gulf is trying to answer these types of question about local populations, including the extent to which they may be resident or transient, their home ranges, and their movements in Alabama and adjacent waters.
What is the greatest threat to the dolphin population in the Northern Gulf?
Our research here in Alabama has found about half of dolphin deaths in our area are linked to human interactions. In fact, this is the most common single known cause of death in the stranded dolphins we recover. Typical human interactions that may cause death include vessel trauma, drowning due to entanglement, and sharp or blunt force trauma.
Another common threat to dolphins in the northern Gulf of Mexico is low salinity due to freshwater discharge. When dolphins experience prolonged freshwater exposure it can cause skin lesions, physiological imbalances, and ultimately death either directly or via secondary illnesses.
Can you characterize the intelligence of dolphins? Is it similar to that of any other species in the animal kingdom?
This is a difficult question because measuring intelligence is inherently biased (the testing is done by humans on a human scale of judgment). Dolphins are known to have complex communication. They are also able to teach and learn skills, such as surgically depredating fish from lines, and to use of ‘tools’ to forage for food. They’ve been documented using sponges as face protection while foraging among corals in Australia.
Can you characterize the dolphin’s faculty of echolocation?
In short, dolphins echolocate by producing short clicks using two air pockets located near their blowhole that are tuned and directed through their bulbous forehead, which is really a large fat deposit called a melon. When the click bounces off something and comes back to the dolphin, it is received into another fat pad in the lower jaw next to the ear where it then travels to and is interpreted by the brain.